I wondered that it might be possible to put something like a two-way hash. The objective is avoiding to store the password in clear. What if someone can access the password field?
This would be something that only knows your PHP code, or a service provided by a third party (a PHP class, etc.), just to put things a bit more difficult to crackers. On the other hand, I think that you could put some asterisks in the WP form displaying the password.
IMHO, these are just 2 small safety measures that can be added to improve safety. Anyway, thank you very much, you saved me a lot of work! I give your plugin 4 stars.